1. Field of the Invention
The present invention relates generally to systems and methods for measuring amplifier performance, and particularly for measuring travelling wave tube amplifier (TWTA) performance in satellite systems.
2. Description of the Related Art
Travelling wave tube amplifiers (TWTA) are a key component for many communication systems. As with many components of communication systems there is a need to monitor and diagnose the operation of the TWTAs in use. There is particularly a need for such techniques in systems which require feedback of TWTA performance characteristics to optimize their operation. Also, TWTA measurements may be useful in communication systems which employ layered modulation, such as described in copending and commonly assigned application Ser. No. 09/844,401, filed on Apr. 27, 2001, by Ernest Chen and entitled “LAYERED MODULATION FOR DIGITAL SIGNALS”, which is hereby incorporated by reference herein, are examples of such systems.
Currently measurements of TWTA performance are obtained by shutting down the transponder service and driving the TWTA at varying input power levels, and measuring amplitude and phase responses as a function of input power level. As it is often desirable to maximize the operating time of the transponders in communication systems, techniques which enable measuring performance of the TWTA while it remains operating are very useful.
In such systems, the TWTA characteristics must be measured while the TWTA operates. The present invention meets the described needs.